int _sumOfLeftLeaves(struct TreeNode* root, int flag)
{
	if (root == NULL)
		return 0;
	if (root->left == NULL && root->right == NULL && flag == 0)
		return root->val;
	return _sumOfLeftLeaves(root->left, 0) + _sumOfLeftLeaves(root->right, 1);
}

int sumOfLeftLeaves(struct TreeNode* root) {
	if (root == NULL)
		return 0;
	if (root->left == NULL && root->right == NULL)
		return 0;
	return _sumOfLeftLeaves(root->left, 0) + _sumOfLeftLeaves(root->right, 1);
}